Synthesis of a 4′,4′-spirothietane-2′, N-cycloadenosine as a highly constrained analogue of 5′-deoxy-5′-methylthioadenosine (MTA)

The synthesis of the highly constrained adenosine derivative 7 featuring at spirothietane at C-4′, which may be considered as a rigid analogue of MTA, is described.     

Modelling subgroup behaviour in crowd dynamics DEM simulation

This paper investigates the behaviour of subgroups in crowd dynamics by means of filming and observation. An existing crowd modelling program, CrowdDMX, based on a discrete element model (DEM) has been modified on the basis of observations made in this paper and literature. Each person is represented as three overlapping circles and motion is modelled in a Newtonian manner. It incorporates psychological forces as well as physical forces in a 2D time-stepping environment. The DEM model was modified to include realistic subgroup behaviour, representing people in the crowd desiring to stay together (families, friends, etc.). Subgroup psychological forces were incorporated. The previous model only simulated individuals moving independently, which was unrealistic in some situations as shown by the observation and filming part of the study. The revised program models subgroups realistically including the tendency to avoid subgroup division in cases of contra-flow.     

Three-body bound states in Amado's model

We have calculated the eigenvalue trajectories of the scattering kernel for a system of three, identical particles with Yamaguchi interactions, for both spin half and spin zero particles. For potential strengths corresponding to large values of the two-body scattering length, we find several, weakly-bound, three-body excited states of the type proposed by Efimov, and calculate their binding energies.     

Synthesis of phospholipids by means of cyclic enediol pyrophosphates : Optically active monovalent and divalent cation salts of diphosphatidylglycerol (Cardiolipin)

A new method for the synthesis of the cardiolipin family of phospholipids which are characteristically located at the inner membrane of mitochondria, and particularly abundant in the heart, is described in this paper. A 1,2-diacyl-sn-glycerol, derived from stearic, palmitic, or myristic acid, is converted into the corresponding 1',3'-diphosphatidylglycerol (DPG), by means of the phosphorylating reagent di(1,2-dimethylethenylene) pyrophosphate in 29%, 23% and 25% overall yields, respectively. The synthesis involves four steps, two of which are carried out in one-flask; only one intermediate and the final product, DPG·2NH₄⁺·2H₂O, are purified, the former by silica gel, and the latter by DEAE-cellulose column chromatography. The ammonium salts are converted into metal ion salts, DPG·2Na⁺· 2H₂O, DPG·Mg²⁺ 2H₂O and DPG·Ca²⁺·2H₂O by metathesis with NaCl, MgCl₂ and CaCl₂, respectively.     

Hosing and sloshing of short-pulse GeV-class wakefield drivers

This Letter examines the electron-hosing instability in relation to the drivers of current and future plasma-wakefield experiments using fully three-dimensional particle-in-cell simulation models. The simulation results are compared to numerical solutions and to asymptotic solutions of the idealized analytic equations. The measured growth rates do not agree with the existing theory and the behavior is shown to depend sensitively on beam length, shape, and charge. We find that even when severe hosing occurs the wake can remain relatively stable.     

The photo-oxidation of solutions of arsenicals to arsenate: A convenient analytical procedure

The separation of arylarsonic acids by HPLC on a reverse-phase C₁₈ column is described. Solutions containing these arsenicals and others such as arsenobetaine are photo-oxidized to arsenate by ultraviolet (UV) radiation (1200 W, 1 h exposure). This allows the analysis of the solution for arsenic by hydride generation techniques. The method, UV HGAA, is developed and applied to the determination of arsenic in the methanol extracts of the Manila clam (Verupis japonica) and the Horse clam (Schizothoerus nutalli).     

Synthesis of the carbon framework of olivin

A convergent synthetic approach is outlined to the tricyclic compound

, which contains the full carbon skeleton of olivin.     

Correlated electromigration of H in the switchable mirror YH(3-delta)

Electromigration of hydrogen in YH(3-delta) is studied by exploiting the H concentration dependence of the optical transmission of YH(3-delta). We find the effective valence Z* of H in YH(3-delta) to be negative. Its value is dominated by a huge wind-force-like term, i.e., Z* approximately K/rho, with K approximately -60 mOmega cm. This value is 3 orders of magnitude larger than typical for H in metals. In an Arrhenius plot, the ratio of hydrogen and electron fluxes extrapolates to unity at infinite temperature, suggesting a one-to-one correlation of hydrogen and electron hopping. We discuss our results in the light of strong electron correlation theories which predict each proton to bind two electrons in a sort of Zhang-Rice singlet.     

Multiple quantum spin counting techniques with quadrupolar nuclei

Phase incremented and continuous irradiation multiple spin correlation methods are applied to spin [Formula: see text] nuclei with small quadrupole couplings such as (7)Li in LiCl and are shown to successfully produce a coherently coupled dipolar spin network. Application to the analogous Na salt shows successful spin correlation evolving at a slower rate due to the weaker homonuclear dipolar coupling strength between Na nuclei. The results are analysed using a statistical approach. Spin counting is non-trivial as not only multiple quantum coherences between spins are generated but also within the quadrupolar spin levels. Na(2)C(2)O(4) is investigated as a material with non-negligible quadrupole coupling and it is in this limit that the spin correlation techniques are found to break down.